Pedicle screw implementation in the spine is a preferred way to provide superior anchorage. Improved deformity correction and overall construct rigidity are two important advantages of pedicle screw instrumentation due its three-column control over the spinal elements. First, pedicle screw instrumentation obviates the need to place instrumentation within the spinal canal with its inherent risk of neurologic injury. Second, the placement of pedicle screws is independent of facet or laminar integrity and thus has been extremely useful in traumatic, neoplastic, and degenerative conditions. The benefit of pedicle screws in the thoracic spine has been tempered by the potential for catastrophic neurological or soft tissue injuries due to the close proximity of these structures. The narrow and inconsistent shape of the thoracic pedicles, especially in spinal deformity, makes their placement technically challenging. As a result, surgeons have employed a number of techniques to ensure the safe and efficacious placement of thoracic pedicle screws. Detailed anatomic landmarks used to determine pedicle location, intraoperative imaging including navigation, and neurophysiological monitoring are some of the techniques currently used by surgeons. The implementation of these techniques and a thorough understanding of the complex three-dimensional anatomy have allowed surgeons to successfully place thoracic and thoracolumbar pedicle screws.
To facilitate accurate placement, a pedicle punch was developed by Castillo, et al as disclosed in U.S. Pat. No. 7,846,164. This device gave the user the ability to create an accurate pilot hole via a pointy tipped punch. This device when used in combination with the x-ray imaging technique facilitated the screw implant procedure in the spine by providing an initial pilot hole.
A secondary advantage was the exposure to radiation from x-ray imaging could be reduced. Castillo, et al noted, “Another drawback of the pedicle screw implant procedure is that the patient, surgeon, and medical staff are exposed to deleterious amounts of radiation, more specifically those deleterious amounts of radiation associated with fluoroscopy during the pedicle screw implant procedure. One way surgeons can protect themselves is with eyewear, thyroid shields, and lead aprons. However, studies with cadavers have shown that the surgeon's hands are still at a high risk of radiation exposure. In one study average fluoroscopy exposure time was 9.3 s per screw. and the average hand dose rate was 58.2 mrem/min. The internationally recommended maximum limit for annual hand radiation exposure is 50,000 mrem. In the same study a significant increase in hand dose rate was noted when placement of the screw was on the same side of the beam source as well as when a heavier cadaver was imaged.”
The use of Castillo, et al's punch device was purported to lower this risk. This prior art punch device while a step forward still was greatly limited in screw placement optimization. The punch simply allowed for a pilot hole to be created at a fixed location. What the surgeon was lacking was the ability to optimally select a preferred location to insert the screw and to do so in a way that minimized bone fracture or damage.
Ideally, the surgeon needed a way to select an optimal location for screw placement based on the images he was seeing prior to fixing the location by creating the punched hole.
The present invention as described as follows provides a guide tool that allows the surgeon to optimally select a location for screw placement, create a secured guided location through which a K-wire placement can be placed to be fixed into the pedicle bone at a location selected by the surgeon.